1. Field of the Invention
The present invention relates to semiconductor devices, and more particularly to a method of manufacturing a semiconductor substrate including a contact having an improved structure and to devices manufactured by such a method.
2. Description of the Related Art
Modern semiconductor devices must have advanced functions such as high response speed and large storage capacity. To meet these functional requirements, semiconductor manufacturing technology has been developed to produce semiconductor devices with highly integrated cells on a chip. The wirings of such semiconductor devices generally are multi-layered structures.
In highly integrated semiconductor devices, contacts are provided to connect the multi-layered wirings. To form such contacts, a contact hole having minimized critical dimension (CD) is formed through an interlayer insulation film formed between an upper wiring and a lower wiring. A conductive material is formed in the contact hole, thereby forming the contact that connects the lower wiring to the upper wiring.
In the process for forming the contact hole through the interlayer dielectric film, a photoresist film is formed on the interlayer insulation film. The photoresist film is exposed and developed to form a photoresist pattern on the interlayer insulation film. The photoresist pattern exposes the portion of the interlayer insulation film where the contact hole will be formed. The exposed portion of the interlayer insulation film is etched using the photoresist pattern as an etching mask, thereby forming the contact hole through the interlayer insulation film. The size of the contact hole becomes minute when the design rule for the semiconductor device is greatly reduced. Thus, the error margin of the photo mask used to form the contact hole considerably decreases in the exposing and developing processes for the photoresist film. As a result, the mis-alignment of the contact hole may very frequently occur during the formation of the contact hole. For example, although the contact hole should be located in the active region of a semiconductor substrate adjacent to a field region of the substrate, the contact hole may be frequently formed in the field region.
A silicide film can be selectively formed on a semiconductor substrate to improve the response speed of the semiconductor device. This silicide film includes a refractory metal having a low specific resistance so that the contact resistance of a contact formed on the silicide film is low even though the contact has a minute dimension in accordance with the reduction of the design rule of the semiconductor device.
The silicide film is generally formed using a silicidation process employing a metal such as titanium (Ti), nickel (Ni), cobalt (Co), etc. After this metal is deposited on an underlying film including silicon, the deposited metal is thermally treated to thereby form the silicide film composed of titanium silicide (TiSi2), nickel silicide (NiSi2), cobalt silicide (CoSi2), etc. on the underlying film. The silicidation process is, for example, disclosed in U.S. Pat. No. 6,015,748 (issued to Kim, et. al.). The cobalt silicide or nickel silicide has a relatively low specific resistance of about 15 to about 20 μΩ·cm. In a semiconductor device having a design rule of below about 0.25 μm, the cobalt silicide is mainly employed since a cobalt silicide film is relatively independent on the critical dimension of a gate structure.
To selectively form the silicide film on the semiconductor substrate, a silicidation blocking layer (SBL) is formed on portions of the substrate or other conductive structures where the silicide film is not formed. That is, the SBL is selectively formed on the portions of the substrate and the conductive structure including silicon while the SBL is not formed on the portions of the substrate and an insulating structure such as the field region and a spacer composed of insulation material without silicon. The SBL is removed after the silicidation process is completed. When the contact hole is formed to expose the portion of the active region having the silicide film thereon, a recess may be formed at the portion of the field region adjacent to the active region because the field region is relatively sensitive to the etching process for the formation of the contact hole. The recess may frequently have a depth of above 10 percent of that of the contact hole, thereby causing the damage to the substrate. Failure of the semiconductor device may occur because a current passing between the active region and the contact may leak through the damaged portion of the substrate. Further, in a semiconductor device having a design rule of below about 0.1 μm, the damage to the substrate becomes more serious at a shallow junction portion thereof so that the damaged portion of the substrate greatly serves as a leakage current source that can cause the device failure. When to prevent the formation of the recess in the field region, the etching process for the contact hole is insufficiently performed, the interlayer insulation film may partially remain in the active region and the contact hole may not be precisely formed on the active region. As a result, the contact formed in the contact hole may not be electrically contacted with the active region, thereby causing the electrical failure of the semiconductor device.